1. Field of the Invention
The present invention relates to an X-ray tube incorporated in an X-ray generator used for a nondestructive inspection of a sample and the like.
2. Related Background Art
As an apparatus for inspecting the internal structure of a sample without destroying the sample, an X-ray generator incorporating therein an X-ray tube for irradiating a sample with an X-ray has conventionally been known in general (see, for example, Japanese Patent Application Laid-Open No. HEI 11-224624). As a part of a nondestructive inspection system for obtaining a fluoroscopic image of a sample, the X-ray generator is used together with an X-ray imaging apparatus (XI) which detects an X-ray transmitted through the sample. As the distance from the X-ray to the sample is shorter, the fluoroscopic image is obtained with a greater magnification.
As the X-ray tube, one comprising an X-ray generating part having a structure in which a target is contained in a tubular part having an X-ray exit window and an electron gun part having a structure in which an electron gun is contained in a tubular part projecting from the periphery of the tubular part of the X-ray generating part has conventionally been known in general (see, for example, Patent Document 2). This X-ray tube is configured such that the target generates an X-ray when the electron gun emits an electron beam thereto, and thus generated X-ray is taken out through the X-ray exit window.
Here, as shown in FIG. 1 of Japanese Patent Application Laid-Open No. HEI 11-224624, the X-ray tube is secured to the housing of the X-ray generator such that the X-ray generating part and the electron gun part are exposed to the outside. As shown in FIG. 5 of Japanese Patent Application Laid-Open No. HEI 11-224624, the X-ray generating part and housing of X-ray generator are formed with slopes for allowing the sample to incline about an axis orthogonal to the X-ray irradiating direction while the sample is disposed near the X-ray exit window of the X-ray tube.
In the conventionally known X-ray tube, an exhaust pipe (tip tube) projects from the peripheral face of the tubular part of the X-ray generating part. Hence, it has been pointed out that the exhaust pipe may hinder the sample or a sample table mounting the sample from greatly inclining about the axis orthogonal to the X-ray irradiating direction while the sample is disposed near the X-ray exit window, which may be problematic when observing a complicated internal structure of the sample three-dimensionally.